(i) Technical Field
The present invention relates to a developing device that develops an electrostatic latent image with a developer including toner and to an image forming apparatus provided with the developing device.
(ii) Related Art
Conventionally, there has been known an image forming apparatuses in which an electrostatic latent image is formed on a surface of an image carrier such as a photoreceptor and is developed with a developer including toner and a magnetic carrier, i.e., charging particles that charge the toner by friction between the magnetic carrier and the toner. The obtained developed image is transferred and fixed onto a sheet, thereby obtaining an image of the fixed image formed on the sheet.
Some of the image forming apparatuses have a developing device provided with a container that contains a developer with toner and a magnetic carrier and a development roll that carries the developer in the container on the surface thereof while rotating. In such a developing device, an agitator provided in the container agitates the developer, which causes friction between the toner and the magnetic carrier. As a result, the toner is charged with a certain polarity while the magnetic carrier is charged with a polarity opposite to that of the toner. Thus, in the developer, the toner is electrostatically attached to the magnetic carrier.
In addition, some of the developing devices are adapted to have a container partitioned into a first chamber and a second chamber and to move and agitate a developer between the first chamber adjacent to a development roll and the second chamber adjacent to the first container.
In such a developing device having a partitioned container, a developer attached to the partition gradually become larger to form lumps and may suddenly collapse due to its tare weight or vibration.
However, the lumped developer attached to the partition includes large amount of toners that have insufficient electrostatic charge due to insufficient agitation in the developer. Thus, sudden collapse of the developer may lead to degraded image quality.